Data Mining: Concepts and Techniques Chapter 1 Introduction

Transcription

1 Data Mining: Concepts and Techniques Chapter 1 Introduction October 25, 2013 Data Mining: Concepts and Techniques 1

2 Chapter 1. Introduction Motivation: Why data mining? What is data mining? Data Mining: On what kind of data? Data mining functionality Classification of data mining systems Top-10 most popular data mining algorithms Major issues in data mining October 25, 2013 Data Mining: Concepts and Techniques 2

3 Why Data Mining? The Explosive Growth of Data: from terabytes to petabytes Data collection and data availability Automated data collection tools, database systems, Web, computerized society Major sources of abundant data Business: Web, e-commerce, transactions, stocks, Science: Remote sensing, bioinformatics, scientific simulation, Society and everyone: news, digital cameras, YouTube We are drowning in data, but starving for knowledge! Necessity is the mother of invention Data mining Automated analysis of massive data sets October 25, 2013 Data Mining: Concepts and Techniques 3

4 Evolution of Sciences Before 1600, empirical science s, theoretical science Each discipline has grown a theoretical component. Theoretical models often motivate experiments and generalize our understanding. 1950s-1990s, computational science Over the last 50 years, most disciplines have grown a third, computational branch (e.g. empirical, theoretical, and computational ecology, or physics, or linguistics.) Computational Science traditionally meant simulation. It grew out of our inability to find closed-form solutions for complex mathematical models now, data science The flood of data from new scientific instruments and simulations The ability to economically store and manage petabytes of data online The Internet and computing Grid that makes all these archives universally accessible Scientific info. management, acquisition, organization, query, and visualization tasks scale almost linearly with data volumes. Data mining is a major new challenge! Jim Gray and Alex Szalay, The World Wide Telescope: An Archetype for Online Science, Comm. ACM, 45(11): 50-54, Nov October 25, 2013 Data Mining: Concepts and Techniques 4

5 Evolution of Database Technology 1960s: 1970s: 1980s: 1990s: 2000s Data collection, database creation, IMS and network DBMS Relational data model, relational DBMS implementation RDBMS, advanced data models (extended-relational, OO, deductive, etc.) Application-oriented DBMS (spatial, scientific, engineering, etc.) Data mining, data warehousing, multimedia databases, and Web databases Stream data management and mining Data mining and its applications Web technology (XML, data integration) and global information systems October 25, 2013 Data Mining: Concepts and Techniques 5

6 What Is Data Mining? Data mining (knowledge discovery from data) Extraction of interesting (non-trivial, implicit, previously unknown and potentially useful) patterns or knowledge from huge amount of data Data mining: a misnomer? Alternative names Knowledge discovery (mining) in databases (KDD), knowledge extraction, data/pattern analysis, data archeology, data dredging, information harvesting, business intelligence, etc. Watch out: Is everything data mining? Simple search and query processing (Deductive) expert systems October 25, 2013 Data Mining: Concepts and Techniques 6

7 Knowledge Discovery (KDD) Process This is a view from typical database systems and data warehousing communities Data mining plays an essential role in the knowledge discovery process Data Mining Pattern Evaluation Task-relevant Data Data Warehouse Selection Data Cleaning Data Integration Databases October 25, 2013 Data Mining: Concepts and Techniques 7

8 KDD Process: An Alternative View Input Data Data Pre- Processing Data Mining Post- Processing Data integration Normalization Feature selection Dimension reduction Pattern discovery Association & correlation Classification Clustering Outlier analysis Pattern evaluation Pattern selection Pattern interpretation Pattern visualization This is a view from typical machine learning and statistics communities October 25, 2013 Data Mining: Concepts and Techniques 8

9 Data Mining and Business Intelligence Increasing potential to support business decisions Decision Making Data Presentation Visualization Techniques Data Mining Information Discovery End User Business Analyst Data Analyst Data Exploration Statistical Summary, Querying, and Reporting Data Preprocessing/Integration, Data Warehouses Data Sources Paper, Files, Web documents, Scientific experiments, Database Systems DBA October 25, 2013 Data Mining: Concepts and Techniques 9

10 Data Mining: Confluence of Multiple Disciplines Machine Learning Pattern Recognition Statistics Applications Data Mining Visualization Algorithm Database Technology High-Performance Computing October 25, 2013 Data Mining: Concepts and Techniques 10

11 Why Not Traditional Data Analysis? Tremendous amount of data Algorithms must be highly scalable to handle such as tera-bytes of data High-dimensionality of data Micro-array may have tens of thousands of dimensions High complexity of data Data streams and sensor data Time-series data, temporal data, sequence data Structure data, graphs, social networks and multi-linked data Heterogeneous databases and legacy databases Spatial, spatiotemporal, multimedia, text and Web data Software programs, scientific simulations New and sophisticated applications October 25, 2013 Data Mining: Concepts and Techniques 11

12 Multi-Dimensional View of Data Mining Data to be mined Relational, data warehouse, transactional, stream, objectoriented/relational, active, spatial, time-series, text, multi-media, heterogeneous, legacy, WWW Knowledge to be mined Characterization, discrimination, association, classification, clustering, trend/deviation, outlier analysis, etc. Multiple/integrated functions and mining at multiple levels Techniques utilized Database-oriented, data warehouse (OLAP), machine learning, statistics, visualization, etc. Applications adapted Retail, telecommunication, banking, fraud analysis, bio-data mining, stock market analysis, text mining, Web mining, etc. October 25, 2013 Data Mining: Concepts and Techniques 12

13 Data Mining: Classification Schemes General functionality Descriptive data mining Predictive data mining Different views lead to different classifications Data view: Kinds of data to be mined Knowledge view: Kinds of knowledge to be discovered Method view: Kinds of techniques utilized Application view: Kinds of applications adapted October 25, 2013 Data Mining: Concepts and Techniques 13

14 Data Mining: On What Kinds of Data? Database-oriented data sets and applications Relational database, data warehouse, transactional database Advanced data sets and advanced applications Data streams and sensor data Time-series data, temporal data, sequence data (incl. bio-sequences) Structure data, graphs, social networks and multi-linked data Object-relational databases Heterogeneous databases and legacy databases Spatial data and spatiotemporal data Multimedia database Text databases The World-Wide Web October 25, 2013 Data Mining: Concepts and Techniques 14

15 Data Mining Functions: (1) Generalization Materials to be covered in Chapters 2-4 Information integration and data warehouse construction Data cleaning, transformation, integration, and multidimensional data model Data cube technology Scalable methods for computing (i.e., materializing) multidimensional aggregates OLAP (online analytical processing) Multidimensional concept description: Characterization and discrimination Generalize, summarize, and contrast data characteristics, e.g., dry vs. wet regions October 25, 2013 Data Mining: Concepts and Techniques 15

16 Data Mining Functions: (2) Association and Correlation Analysis (Chapter 5) Frequent patterns (or frequent itemsets) What items are frequently purchased together in your Walmart? Association, correlation vs. causality A typical association rule Diaper Beer [0.5%, 75%] (support, confidence) Are strongly associated items also strongly correlated? How to mine such patterns and rules efficiently in large datasets? How to use such patterns for classification, clustering, and other applications? October 25, 2013 Data Mining: Concepts and Techniques 16

17 Data Mining Functions: (3) Classification and Prediction (Chapter 6) Classification and prediction Construct models (functions) based on some training examples Describe and distinguish classes or concepts for future prediction E.g., classify countries based on (climate), or classify cars based on (gas mileage) Predict some unknown or missing numerical values Typical methods Decision trees, naïve Bayesian classification, support vector machines, neural networks, rule-based classification, patternbased classification, logistic regression, Typical applications: Credit card fraud detection, direct marketing, classifying stars, diseases, web-pages, October 25, 2013 Data Mining: Concepts and Techniques 17

18 Data Mining Functions: (4) Cluster and Outlier Analysis (Chapter 7) Cluster analysis Unsupervised learning (i.e., Class label is unknown) Group data to form new categories (i.e., clusters), e.g., cluster houses to find distribution patterns Principle: Maximizing intra-class similarity & minimizing interclass similarity Many methods and applications Outlier analysis Outlier: A data object that does not comply with the general behavior of the data Noise or exception? One person s garbage could be another person s treasure Methods: by product of clustering or regression analysis, Useful in fraud detection, rare events analysis October 25, 2013 Data Mining: Concepts and Techniques 18

19 Data Mining Functions: (5) Trend and Evolution Analysis (Chapter 8) Sequence, trend and evolution analysis Trend and deviation analysis: e.g., regression Sequential pattern mining e.g., first buy digital camera, then large SD memory cards Periodicity analysis Motifs, time-series, and biological sequence analysis Approximate and consecutive motifs Similarity-based analysis Mining data streams Ordered, time-varying, potentially infinite, data streams October 25, 2013 Data Mining: Concepts and Techniques 19

20 Data Mining Functions: (6) Structure and Network Analysis (Chapter 9) Graph mining Finding frequent subgraphs (e.g., chemical compounds), trees (XML), substructures (web fragments) Information network analysis Social networks: actors (objects, nodes) and relationships (edges) e.g., author networks in CS, terrorist networks Multiple heterogeneous networks A person could be multiple information networks: friends, family, classmates, Links carry a lot of semantic information: Link mining Web mining Web is a big information network: from PageRank to Google Analysis of Web information networks Web community discovery, opinion mining, usage mining, October 25, 2013 Data Mining: Concepts and Techniques 20

21 Major Challenges in Data Mining Efficiency and scalability of data mining algorithms Parallel, distributed, stream, and incremental mining methods Handling high-dimensionality Handling noise, uncertainty, and incompleteness of data Incorporation of constraints, expert knowledge, and background knowledge in data mining Pattern evaluation and knowledge integration Mining diverse and heterogeneous kinds of data: e.g., bioinformatics, Web, software/system engineering, information networks Application-oriented and domain-specific data mining Invisible data mining (embedded in other functional modules) Protection of security, integrity, and privacy in data mining October 25, 2013 Data Mining: Concepts and Techniques 21

22 Why Data Mining? Potential Applications Data analysis and decision support Market analysis and management Target marketing, customer relationship management (CRM), market basket analysis, cross selling, market segmentation Risk analysis and management Forecasting, customer retention, improved underwriting, quality control, competitive analysis Fraud detection and detection of unusual patterns (outliers) Other Applications Text mining (news group, , documents) and Web mining Stream data mining Bioinformatics and bio-data analysis October 25, 2013 Data Mining: Concepts and Techniques 22

23 Ex. 1: Market Analysis and Management Where does the data come from? Credit card transactions, loyalty cards, discount coupons, customer complaint calls, plus (public) lifestyle studies Target marketing Find clusters of model customers who share the same characteristics: interest, income level, spending habits, etc. Determine customer purchasing patterns over time Cross-market analysis Find associations/co-relations between product sales, & predict based on such association Customer profiling What types of customers buy what products (clustering or classification) Customer requirement analysis Identify the best products for different groups of customers Predict what factors will attract new customers Provision of summary information Multidimensional summary reports Statistical summary information (data central tendency and variation) October 25, 2013 Data Mining: Concepts and Techniques 23

24 Ex. 2: Corporate Analysis & Risk Management Finance planning and asset evaluation cash flow analysis and prediction contingent claim analysis to evaluate assets cross-sectional and time series analysis (financial-ratio, trend analysis, etc.) Resource planning summarize and compare the resources and spending Competition monitor competitors and market directions group customers into classes and a class-based pricing procedure set pricing strategy in a highly competitive market October 25, 2013 Data Mining: Concepts and Techniques 24

25 Ex. 3: Fraud Detection & Mining Unusual Patterns Approaches: Clustering & model construction for frauds, outlier analysis Applications: Health care, retail, credit card service, telecomm. Auto insurance: ring of collisions Money laundering: suspicious monetary transactions Medical insurance Professional patients, ring of doctors, and ring of references Unnecessary or correlated screening tests Telecommunications: phone-call fraud Phone call model: destination of the call, duration, time of day or week. Analyze patterns that deviate from an expected norm Retail industry Analysts estimate that 38% of retail shrink is due to dishonest employees Anti-terrorism October 25, 2013 Data Mining: Concepts and Techniques 25

26 KDD Process: Several Key Steps Learning the application domain relevant prior knowledge and goals of application Creating a target data set: data selection Data cleaning and preprocessing: (may take 60% of effort!) Data reduction and transformation Find useful features, dimensionality/variable reduction, invariant representation Choosing functions of data mining summarization, classification, regression, association, clustering Choosing the mining algorithm(s) Data mining: search for patterns of interest Pattern evaluation and knowledge presentation visualization, transformation, removing redundant patterns, etc. Use of discovered knowledge October 25, 2013 Data Mining: Concepts and Techniques 26

27 Are All the Discovered Patterns Interesting? Data mining may generate thousands of patterns: Not all of them are interesting Suggested approach: Human-centered, query-based, focused mining Interestingness measures A pattern is interesting if it is easily understood by humans, valid on new or test data with some degree of certainty, potentially useful, novel, or validates some hypothesis that a user seeks to confirm Objective vs. subjective interestingness measures Objective: based on statistics and structures of patterns, e.g., support, confidence, etc. Subjective: based on user s belief in the data, e.g., unexpectedness, novelty, actionability, etc. October 25, 2013 Data Mining: Concepts and Techniques 27

28 Find All and Only Interesting Patterns? Find all the interesting patterns: Completeness Can a data mining system find all the interesting patterns? Do we need to find all of the interesting patterns? Heuristic vs. exhaustive search Association vs. classification vs. clustering Search for only interesting patterns: An optimization problem Can a data mining system find only the interesting patterns? Approaches First general all the patterns and then filter out the uninteresting ones Generate only the interesting patterns mining query optimization October 25, 2013 Data Mining: Concepts and Techniques 28

29 Other Pattern Mining Issues Precise patterns vs. approximate patterns Association and correlation mining: possible find sets of precise patterns But approximate patterns can be more compact and sufficient How to find high quality approximate patterns?? Gene sequence mining: approximate patterns are inherent How to derive efficient approximate pattern mining algorithms?? Constrained vs. non-constrained patterns Why constraint-based mining? What are the possible kinds of constraints? How to push constraints into the mining process? October 25, 2013 Data Mining: Concepts and Techniques 29

30 Why Data Mining Query Language? Automated vs. query-driven? Finding all the patterns autonomously in a database? unrealistic because the patterns could be too many but uninteresting Data mining should be an interactive process User directs what to be mined Users must be provided with a set of primitives to be used to communicate with the data mining system Incorporating these primitives in a data mining query language More flexible user interaction Foundation for design of graphical user interface Standardization of data mining industry and practice October 25, 2013 Data Mining: Concepts and Techniques 30

31 Primitives that Define a Data Mining Task Task-relevant data Database or data warehouse name Database tables or data warehouse cubes Condition for data selection Relevant attributes or dimensions Data grouping criteria Type of knowledge to be mined Characterization, discrimination, association, classification, prediction, clustering, outlier analysis, other data mining tasks Background knowledge Pattern interestingness measurements Visualization/presentation of discovered patterns October 25, 2013 Data Mining: Concepts and Techniques 31

32 Primitive 3: Background Knowledge A typical kind of background knowledge: Concept hierarchies Schema hierarchy E.g., street < city < province_or_state < country Set-grouping hierarchy E.g., {20-39} = young, {40-59} = middle_aged Operation-derived hierarchy address: [email protected] login-name < department < university < country Rule-based hierarchy low_profit_margin (X) <= price(x, P 1 ) and cost (X, P 2 ) and (P 1 - P 2 ) < $50 October 25, 2013 Data Mining: Concepts and Techniques 32

33 Primitive 4: Pattern Interestingness Measure Simplicity e.g., (association) rule length, (decision) tree size Certainty e.g., confidence, P(A B) = #(A and B)/ #(B), classification reliability or accuracy, certainty factor, rule strength, rule quality, discriminating weight, etc. Utility potential usefulness, e.g., support (association), noise threshold (description) Novelty not previously known, surprising (used to remove redundant rules, e.g., Illinois vs. Champaign rule implication support ratio) October 25, 2013 Data Mining: Concepts and Techniques 33

34 Primitive 5: Presentation of Discovered Patterns Different backgrounds/usages may require different forms of representation E.g., rules, tables, crosstabs, pie/bar chart, etc. Concept hierarchy is also important Discovered knowledge might be more understandable when represented at high level of abstraction Interactive drill up/down, pivoting, slicing and dicing provide different perspectives to data Different kinds of knowledge require different representation: association, classification, clustering, etc. October 25, 2013 Data Mining: Concepts and Techniques 34

35 DMQL A Data Mining Query Language Motivation A DMQL can provide the ability to support ad-hoc and interactive data mining By providing a standardized language like SQL Hope to achieve a similar effect like that SQL has on relational database Foundation for system development and evolution Facilitate information exchange, technology transfer, commercialization and wide acceptance Design DMQL is designed with the primitives described earlier October 25, 2013 Data Mining: Concepts and Techniques 35

36 An Example Query in DMQL October 25, 2013 Data Mining: Concepts and Techniques 36

37 Other Data Mining Languages & Standardization Efforts Association rule language specifications MSQL (Imielinski & Virmani 99) MineRule (Meo Psaila and Ceri 96) Query flocks based on Datalog syntax (Tsur et al 98) OLEDB for DM (Microsoft 2000) and recently DMX (Microsoft SQLServer 2005) Based on OLE, OLE DB, OLE DB for OLAP, C# Integrating DBMS, data warehouse and data mining DMML (Data Mining Mark-up Language) by DMG ( Providing a platform and process structure for effective data mining Emphasizing on deploying data mining technology to solve business problems October 25, 2013 Data Mining: Concepts and Techniques 37

38 Integration of Data Mining and Data Warehousing Data mining systems, DBMS, Data warehouse systems coupling No coupling, loose-coupling, semi-tight-coupling, tight-coupling On-line analytical mining data integration of mining and OLAP technologies Interactive mining multi-level knowledge Necessity of mining knowledge and patterns at different levels of abstraction by drilling/rolling, pivoting, slicing/dicing, etc. Integration of multiple mining functions Characterized classification, first clustering and then association October 25, 2013 Data Mining: Concepts and Techniques 38

39 Coupling Data Mining with DB/DW Systems No coupling flat file processing, not recommended Loose coupling Fetching data from DB/DW Semi-tight coupling enhanced DM performance Provide efficient implement a few data mining primitives in a DB/DW system, e.g., sorting, indexing, aggregation, histogram analysis, multiway join, precomputation of some stat functions Tight coupling A uniform information processing environment DM is smoothly integrated into a DB/DW system, mining query is optimized based on mining query, indexing, query processing methods, etc. October 25, 2013 Data Mining: Concepts and Techniques 39

40 Architecture: Typical Data Mining System Graphical User Interface Pattern Evaluation Data Mining Engine Database or Data Warehouse Server Knowl edge- Base data cleaning, integration, and selection Database Data Warehouse World-Wide Web Other Info Repositories October 25, 2013 Data Mining: Concepts and Techniques 40